"Gate passes" are issued by the individual air carriers at their discretion. Typically, these passes are given to those persons escorting unaccompanied minors or passengers with special needs. You will need to request this "gate pass" at the airline ticket counter. Please note that a government issued, photo ID is required to in order to acquire this pass. Any specific questions regarding obtaining the "gate pass/escort pass" should be directed to the Airlines.
What is the procedure for picking up an unaccompanied minor from the airport?